CVE-2026-99128 sctp: validate chunk length in the inqueue parser
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99128?
CVE-2026-99128 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
sctp: validate chunk length in the inqueue parser
SCTP chunks always include a four-byte generic header, but sctp_inq_pop() currently accepts shorter declared lengths. A zero-length chunk leaves chunk_end at the current header.
When ASCONF is covered by the association's SCTP-AUTH policy, sctp_assoc_bh_rcv() can continue before the state machine performs its normal chunk-length check. sctp_inq_pop() then returns the same malformed chunk repeatedly and the receive softirq can lock up.
A remote SCTP peer can trigger this after establishing an association on a kernel built with CONFIG_IP_SCTP and configured with net.sctp.addip_enable=1 and net.sctp.auth_enable=1. The reproducer did not require application credentials, a shared SCTP AUTH key, or net.sctp.addip_noauth_enable=1.
On commit f967455fb2a5 ("seg6: reset IP6CB after IPv6 decapsulation"), one zero-length ASCONF caused repeated watchdog soft-lockup reports in a two-vCPU KVM guest. All 3 pre-trigger health probes succeeded, while 36 of 37 post-trigger probes failed. With this change, all 37 post-trigger probes succeeded and no equivalent soft-lockup signature appeared.
Reject chunks shorter than the generic SCTP header at the shared inqueue parser boundary. Mark the packet for discard before either caller can continue processing it, while preserving the four-byte generic minimum. Declared-length 1 through 4 controls and kernel-generated ASCONF traffic remained healthy. The patched sctp_hello selftest passed for IPv4 and IPv6.
The complete private reproducer and validation evidence are available directly to maintainers on request.
Which versions are affected by CVE-2026-99128?
How do I fix CVE-2026-99128?
Upgrade to a fixed version.
Is CVE-2026-99128 being exploited?
There is no known exploitation of CVE-2026-99128 in the wild and no public exploit code.
Sources
Also known as AZL-111239, BELL-CVE-2026-99128, DEBIAN-CVE-2026-99128, GHSA-c382-phc9-mxqc, UBUNTU-CVE-2026-99128.